JP3837347B2 - Power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power steering apparatus provided with a sliding valve.
[0002]
[Prior art]
In the conventional example shown in FIG. 3, a sector gear 2 is incorporated in the housing 1, and the sector gear 2 is linked to a wheel via a pitman arm (not shown). An input shaft 3 linked to a handle (not shown) is inserted into the housing 1, and a ball screw 4 having a predetermined lead angle is formed on the input shaft 3.
A ball nut 5 is provided coaxially with the input shaft 3, and a plurality of balls 7 circulated by a ball tube 6 are interposed between the ball nut 5 and the ball screw 4. The rack 8 formed on the ball nut 5 is meshed with the teeth 2a of the sector gear 2 so that a handle (not shown) is mechanically linked to the wheel side.
[0003]
A plug 9 is fixed to one end of the housing 1, and a bearing 10 is provided in the plug 9. The bearing 10 supports the input shaft 3 so as to be rotatable and slidable in the axial direction.
Further, a seal member 14 is provided in the plug 9 and the fluid in the housing 1 is prevented from leaking by the seal member 14.
On the other hand, the input shaft 3 is also supported by a bearing 16 provided between the input shaft 3 and the housing 1. The bearing 16 also supports the input shaft 3 in a freely rotatable manner and can also slide in the axial direction.
In addition, grease 15 is filled between the outer periphery of the input shaft 3 and the plug 9, and the input shaft 3 moves smoothly in the axial direction by the grease 15.
[0004]
A thrust washer 17 is provided on the input shaft 3, and the thrust washer 17 is disposed so as to be flush with the other end surface of the housing 1. A spool 18 is provided on the outer peripheral surface of the input shaft 3 that protrudes from the other end surface of the housing 1, and one end thereof is brought into contact with the thrust washer 17.
A cylindrical valve body 19 is fixed to the other end of the housing 1, and the valve body 19 includes an outer portion 20 having the same length as the spool 18 and an inner portion 21 having a length shorter than the spool 18. ing. The spool 18 is slidably incorporated in the inner portion 21. Further, when the spool 18 is incorporated in this way, a gap 22 is formed between the thrust washer 17 and the inner portion 21.
[0005]
Further, another thrust washer 23 is provided on the input shaft 3, and the other end of the spool 18 is brought into contact with the thrust washer 23. Accordingly, the spool 18 is put between the thrust washers 17 and 23, and a gap 24 is also formed between the thrust washer 23 and the inner portion 21.
A cover 25 is fixed to the end of the valve body 19. At this time, the thrust washer 23 is arranged on the same surface as the valve body 19 fixing surface of the cover 25.
Further, the inside of the cover 25 is connected to a tank via a pipe or the like (not shown). The inside of the cover 25 is a low pressure chamber 11.
Further, in a space surrounded by the housing 1, the plug 9, and the input shaft 3, and a space in which the sector gear 2 communicating with this space through a gap between the inner race and the outer race constituting the bearing 16 is arranged. Similarly to the inside of the cover 25, these are connected to the tank via a pipe (not shown), and both the spaces are used as the low pressure chamber 40.
[0006]
A spring hole 26 is formed in the valve body 19 so as to extend over the outer portion 20 and the inner portion 21. A centering spring 27 is provided in the spring hole 26, one end of which is in contact with the end of the housing 1 and the thrust washer 17, and the other end is in contact with the end of the cover 25 and the thrust washer 23. . Therefore, the spool 18 maintains the neutral position shown in FIG. 3 by the elastic force of the centering spring 27. When the input shaft 3 moves in the axial direction, the spool 18 moves in the inner portion 21 against the centering spring 27. However, the stroke amount is regulated within the range of the gaps 22 and 24. Thus, the inner part 21 of the valve body 19 and the spool 18 slidably incorporated in the inner part 21 are combined to constitute a sliding valve V as a control valve.
Note that the thrust washer 17 and the thrust washer 23 generally have the same outer diameter.
[0007]
A power cylinder (not shown) is connected to the sliding valve V. The operation of the power cylinder is controlled by switching the sliding valve V. Thereby, the wheel is steered by assisting the rotation operation of the sector gear 2.
[0008]
Next, the operation of this conventional apparatus will be described.
When the handle is not rotated, the sliding valve V maintains the neutral position shown in the figure. If the sliding valve V is in the neutral position in this way, no pressure oil is supplied to the power cylinder.
On the other hand, when the handle is rotated, the input shaft 3 rotates, and the rotational force is transmitted from the ball screw 4 to the ball nut 5 via the ball 7. The ball nut 5 is engaged with the sector gear 2. Therefore, since the movement of the sector gear 2 in the rotational direction is normally suppressed by the grounding resistance on the wheel side, the movement of the ball nut 5 is restricted, and the rotational force is a reaction force via the ball nut 5. Acts on the ball screw 4, that is, the input shaft 3. The reaction force causes the input shaft 3 to move in the axial direction while rotating along the lead angle of the ball screw 4.
[0009]
When the input shaft 3 moves in the axial direction in this way, the spool 18 slides in the inner portion 21 and the sliding valve V is switched. And the power cylinder which is not shown in figure operates.
[0010]
[Problems to be solved by the invention]
In the above-described conventional apparatus, the low pressure chamber 11 in the cover 25 is communicated with the tank via a pipe or the like, but the pressure in the low pressure chamber 11 slightly increases by the amount of pipe resistance generated in the pipe or the like. . The slightly increased pressure in the low pressure chamber 11 acts on the input shaft 3 and the end face of the thrust washer 23. On the other hand, the same pressure as that of the low-pressure chamber 11 is also introduced to the low-pressure chamber 40 on the opposite side across the low-pressure chamber 11 and the sliding valve V. On the low-pressure chamber 40 side, the input shaft 3 has an end face. Therefore, the pressure in the low pressure chamber 40 acts only on the thrust washer 17. Therefore, a thrust in the right direction in the figure acts on the input shaft 3 due to the difference in the area difference on which the pressure acts. When such a thrust acts on the input shaft, the magnitude of the applied force differs between when the sliding valve V is switched to the right and when it is switched to the left. That is, when the sliding shaft V is switched by moving the input shaft 3 to the right, the thrust from the low pressure chamber 11 side is applied to the input shaft 3 by an amount corresponding to the cross-sectional area of the seal member 14 portion of the input shaft 3. The power is small and sufficient. On the other hand, when switching the sliding valve V by moving the input shaft 3 in the left direction, it is necessary to increase the thrust corresponding to the cross-sectional area of the seal member 14 portion of the input shaft 3 generated on the low pressure chamber 40 side. Therefore, the applied force must be increased.
[0011]
Thus, the difference in force generated according to the switching direction of the sliding valve V is not so large. However, when the diameter of the handle linked to the input shaft 3 is reduced or the back pressure is increased, the difference in force is increased. Amplified. For this reason, there is a problem in that the difference in steering force between when the vehicle is steered to the right and when the vehicle is steered to the left is unbalanced, giving the driver an uncomfortable feeling.
An object of the present invention is to obtain a power steering device in which a difference in steering force does not occur depending on a steering direction.
[0012]
[Means for Solving the Problems]
The first invention includes a housing, an end inserted into the housing, an input shaft that can rotate and move in the axial direction with respect to the housing, a penetrating through the one end of the input shaft, A power steering device comprising a sliding valve that moves in synchronization with the input shaft, and a control valve that is configured by a housing that is opposed to the sliding valve in the radial direction so that both ends of the control valve communicate with the tank side The sliding valve is provided with an elastic body that applies an elastic force in the axial direction to the sliding valve on one side surface, and is always applied to the input shaft by the pressure guided to the control valve in the housing. Axial thrust acting in one direction is canceled by the initial set load of the elastic body Characterized in that the configuration that.
[0013]
According to a second aspect of the present invention, in the first aspect of the invention, the outer periphery of one end of the elastic body that contacts the housing side is fitted to the housing, thereby preventing the radial movement of the elastic body relative to the housing. Features.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The first embodiment shown in FIG. 1 is characterized in that a conical coil spring S corresponding to the elastic body of the present invention is interposed between a thrust washer 17 and a housing 1, and other configurations are the same as the conventional example. Is exactly the same. Therefore, the same components as those in the conventional example are denoted by the same reference numerals, and detailed description thereof is omitted.
[0015]
The conical coil spring S has one end with a large diameter pressed against the corner of the recess 1 a formed in the housing 1 and the other end with a small diameter pressed against the thrust washer 17. By arranging the conical coil spring S without rattling in the recess 1 a of the housing 1 in this way, the initial set load of the conical coil spring S is applied to the thrust washer 17 without variation.
On the thrust washer 17 side, the conical coil spring R contacts only the thrust washer 17 and does not contact the housing 1 side. By doing so, the hysteresis of the initial set load of the conical coil spring S is eliminated, and this initial set load acts effectively on the thrust washer 17.
[0016]
The conical coil spring S thus configured determines its initial load as follows. As described above, the thrust in the right direction in the drawing is constantly acting on the input shaft 3 due to the pressure action of the low pressure chambers 11 and 40 caused by the pressure loss of the piping. The magnitude of the thrust that always acts in the right direction with respect to the input shaft 3 is obtained by multiplying the pressure in the low pressure chamber 11 by the cross-sectional area of the input shaft 3 that is disconnected from the outside by the seal member 14. It is. Therefore, in this embodiment, the pressure generated in the low pressure chamber 11 is measured, and the thrust acting on the input shaft 3 is obtained in advance. And the initial set load of a conical coil spring is set to the magnitude | size equal to this calculated | required thrust.
[0017]
If the initial set load of the conical coil spring S is set as described above, the thrust acting on the input shaft 3 due to the pressure in the low pressure chambers 11 and 40 is canceled. Therefore, the magnitude of the applied force is equal between when the sliding valve V is switched to the right and when it is switched to the left. Therefore, the steering torque when operating the steering wheel in the right direction is equal to the steering torque when operating the steering wheel in the left direction, and it is possible to prevent the driver from feeling uncomfortable.
[0018]
In the second embodiment shown in FIG. 2, a power cylinder is incorporated in the housing 1. Since the other configuration is the same as that of the first embodiment, the same components are denoted by the same reference numerals, and the difference from the first embodiment will be mainly described.
A ball nut 30 is slidably incorporated in the housing 1. A rack 8 is also formed on the ball nut 30, and the rack 8 is engaged with the teeth 2 a of the sector gear 2. Further, the rotational force of the input shaft 3 is transmitted to the ball nut 30 via the ball 7.
[0019]
The ball nut 30 thus configured is provided with the seal member 31 on the outer periphery thereof, thereby ensuring the sealing performance with the housing 1, and is provided with the seal member 35 on the inner periphery thereof so that the ball nut 30 is connected to the input shaft 3. Sealing performance is ensured. On the other hand, the housing 1 is provided with a sealing member 36 to ensure a sealing property with the input shaft 3. The seal members 31, 35, and 36 and the seal member 14 define a first pressure chamber 32 and a second pressure chamber 33 in the housing 1 to constitute a power cylinder PS.
[0020]
A sliding valve V is connected to the first and second pressure chambers 32 and 33 of the power cylinder through an oil passage (not shown). The movement of the power cylinder is controlled in accordance with the switching direction of the sliding valve V. Further, when the ball nut 30 having the piston function is actuated in this manner, the sector gear 2 meshing therewith rotates and the wheel is steered.
[0021]
Also in the second embodiment thus configured, the conical coil spring S is interposed between the thrust washer 17 and the housing 1 as in the first embodiment. Then, by applying the initial set load of the elastic body to the input shaft 3, the thrust in the right direction of the drawing generated in the input shaft 3 by the pressure in the low pressure chambers 11 and 40 is canceled.
Therefore, the magnitude of the applied force is equal between when the sliding valve V is switched to the right and when it is switched to the left, so that the driver does not feel uncomfortable.
[0022]
In the first and second embodiments, the conical coil spring S is used. However, instead of the conical coil spring S, a normal coil spring or a leaf spring may be used. In other words, any elastic body may be used as long as it applies an initial load to the input shaft 3.
In the first and second embodiments, the elastic body made of the conical coil spring S is provided between the thrust washer 17 and the housing 1, but a force for canceling the thrust acting from the low pressure chamber 11 side is input. The elastic body may be provided at any position as long as it can act on the shaft 3. For example, an elastic body may be provided on the input shaft 3 outside the housing 1.
[0023]
Further, in the first and second embodiments, the power steering device using the ball nut has been described. However, the present invention can also be used for a power steering device using an acme screw instead of the ball nut.
[0024]
【The invention's effect】
According to the present invention, the axial thrust that always acts in one direction with respect to the input shaft by the pressure introduced to both ends of the control valve in the housing is canceled by the initial set load of the elastic body. The steering force is the same when steered and steered leftward.
Therefore, it is possible to prevent the driver from feeling uncomfortable during steering.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a first embodiment.
FIG. 2 is a cross-sectional view of a second embodiment.
FIG. 3 is a cross-sectional view of a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Housing 3 Input shaft 14 Seal member V Sliding valve S Conical coil spring corresponded to the elastic body of this invention

Claims (2)

A housing, one end inserted into the housing, an input shaft that can rotate and move in the axial direction with respect to the housing, a penetrating through the one end of the input shaft, and synchronized with the input shaft In a power steering apparatus comprising a sliding valve that moves, a control valve is configured by a housing that is disposed opposite to the sliding valve in a radial direction, and both ends of the control valve communicate with the tank side. An elastic body that provides an axial elastic force to the sliding valve is provided on one of the side surfaces, and it always acts in one direction on the input shaft by the pressure guided to the control valve in the housing. The axial thrust is canceled by the initial set load of the elastic body. Power steering apparatus according to claim and. 2. The power steering apparatus according to claim 1, wherein the outer periphery of one end of the elastic body abutting on the housing side is fitted into the housing to prevent the elastic body from shaking in the radial direction with respect to the housing.

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